Backed out changeset bc9031f59e1c (bug 1021248) for Werror bustage

gfx/layers/client/TiledContentClient.cpp

@@ -120,6 +120,8 @@ TiledContentClient::UseTiledLayerBuffer(TiledBufferType aType)
 }
 
 SharedFrameMetricsHelper::SharedFrameMetricsHelper()
+  : mLastProgressiveUpdateWasLowPrecision(false)
+  , mProgressiveUpdateWasInDanger(false)
 {
   MOZ_COUNT_CTOR(SharedFrameMetricsHelper);
 }
@@ -163,6 +165,17 @@ SharedFrameMetricsHelper::UpdateFromCompositorFrameMetrics(
   aCompositionBounds = ParentLayerRect(compositorMetrics.mCompositionBounds);
   aZoom = compositorMetrics.GetZoomToParent();
 
+  // Reset the checkerboard risk flag when switching to low precision
+  // rendering.
+  if (aLowPrecision && !mLastProgressiveUpdateWasLowPrecision) {
+    // Skip low precision rendering until we're at risk of checkerboarding.
+    if (!mProgressiveUpdateWasInDanger) {
+      return true;
+    }
+    mProgressiveUpdateWasInDanger = false;
+  }
+  mLastProgressiveUpdateWasLowPrecision = aLowPrecision;
+
   // Always abort updates if the resolution has changed. There's no use
   // in drawing at the incorrect resolution.
   if (!FuzzyEquals(compositorMetrics.GetZoom().scale, contentMetrics.GetZoom().scale)) {
@@ -184,8 +197,11 @@ SharedFrameMetricsHelper::UpdateFromCompositorFrameMetrics(
 
   // When not a low precision pass and the page is in danger of checker boarding
   // abort update.
-  if (!aLowPrecision && AboutToCheckerboard(contentMetrics, compositorMetrics)) {
-    return true;
+  if (!aLowPrecision && !mProgressiveUpdateWasInDanger) {
+    if (AboutToCheckerboard(contentMetrics, compositorMetrics)) {
+      mProgressiveUpdateWasInDanger = true;
+      return true;
+    }
   }
 
   // Abort drawing stale low-precision content if there's a more recent